This invention relates to an automatically regulated belt stretching device.
It is known that the transmission of motion from the drive shaft to the cam shafts is effected by means of cogged belts manufactured in such a way that after an initial permanent set, they become virtually nondeformable.
The engine casings produced today are manufactured from light aluminium alloys having a high coefficient of thermal expansion.
Consequently, during the operation of an engine and as a result of the variations in temperature to which the engine is subjected, there are considerable variations in the distance between the centres of the shafts on which the belt operates.
These variations occur as the engine passes from a heating phase to a temperature control phase and then to the cooling phase following stoppage of the engine. These variations then lead to substantial changes with respect to the initial tension of the belt and thus to disadvantages during the operation thereof, such as noise and excessive or insufficient tension.
Hydraulically operated stretchers using the engine oil are known, which, in spite of the accuracy of assembly and construction, may have operating defects, such as oil losses, noise, possible seizure and high costs.